[bugfix] Fix PBS scheduler regex for negative values

[thilinarmtb]

The current regex used in the PBS scheduler can't capture negative exit codes.
See here. This PR fixes it. Coauthored by @colleeneb.

[TApplencourt]

Just to add some context, yes PBS use negative exit code... https://www.nas.nasa.gov/hecc/support/kb/pbs-exit-codes_185.html

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.24%. Comparing base (6ca5b9c) to head (63d2c7c).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #3571   +/-   ##
========================================
  Coverage    91.24%   91.24%           
========================================
  Files           62       62           
  Lines        13531    13531           
========================================
  Hits         12347    12347           
  Misses        1184     1184           

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